Prolongation of the QT interval in primary aldosteronism.

1. Only limited information is available concerning the changes in the electrocardiogram in primary aldosteronism. The aim of the present study was to determine factors influencing the QTc interval in patients with primary aldosteronism. 2. Nineteen patients with primary aldosteronism caused by a Conn's adenoma and 69 patients with essential hypertension, in whom all possible causes of secondary hypertension had been excluded, were included in the present study. Before and 10-20 days after adrenalectomy, blood and electrocardiographic examinations were conducted. 3. Systolic and diastolic blood pressures in primary aldosteronism were found to be comparable to those in essential hypertension. However, the QTc interval was significantly prolonged and serum potassium concentrations were significantly decreased in patients with primary aldosteronism compared with patients with essential hypertension (492.7+/-20.3 vs 428.5+/-3.1 msec for QTc interval, respectively (P<0.01); 3.07+/-0.12 vs 4.07+/-0.05 mEq/L for serum potassium concentrations, respectively (P<0.01)). The QTc interval was significantly correlated with serum potassium concentrations in primary aldosteronism (P=0.0011; r=-0.6902), but not in patients with essential hypertension. 4. Blood pressure significantly decreased after adrenalectomy. Furthermore, serum potassium concentrations increased significantly and did not correlate with the QTc interval after adrenalectomy (P=0.54; r=-0.1500). 5. Our results indicate that the QTc interval is prolonged in patients with primary aldosteronism, probably owing to hypokalaemia.